<style>
	.box1 {
		width: 100px;
		height: 100px;
		float: left;
		border: 1px solid #000;
	}

	.box2 {
		width: 100px;
		height: 100px;
		float: left;
		border: 1px solid #000;
	}

	.box {
		background: yellow
	}
</style>

<body>
	<div class="box">
		<div class="box1"></div>
		<div class="box2"></div>
		<div style="clear: both;"></div>
	</div>
</body>